The invention is concerned with a glazing having antennas and a means of electrical connection to an external circuit.
Antennas are incorporated into glazings in buildings and in vehicles.
The number of antennas in automotive glazing is increasing due to the demand for more communication systems in vehicles. The state of the art for communication systems in vehicles includes radio (AM, FM), digital audio broadcasting (DAB), television (TV), digital video broadcasting-terrestrial (DVB-t), telephone (GSM), navigation (GPS), WLAN, remote keyless entry (RKE), car-to-car communication and car-to-infrastructure communication (car2X) and paging systems.
A means of electrical connection to an external circuit may be provided by, for example, a surface contact, which may be linear or a two dimensional sheet, made of conductive material (metal, film or coating).
A coupling electrode may be positioned in direct current isolation from the surface contact such that only alternating current coupling occurs between the surface contact and the coupling electrode. The coupling electrode may be applied as a wire on the surface of, or embedded in, a layer of plastic material in laminated glass or a bi-layer glazing.
At least one antenna may be in direct current contact with the coupling electrode. The antenna may be arranged on a surface of the glazing
U.S. Pat. No. 8,077,100 discloses a glazing comprising a surface contact, a coupling electrode and an antenna.
According to this prior art, improved performance of the connection between the surface contact and the antenna may be achieved for a particular frequency of alternating current when the coupling electrode length is approximately equal to an odd multiple of a quarter of the effective wavelength Lambda Effective in the glazing corresponding to frequency f, where f is the frequency of the signal received by the antenna.
U.S. Pat. No. 8,077,100 further discloses three embodiments having more than one antenna.
In the first embodiment, a broadband antenna is provided, comprising a surface contact and two antennas, one at each end of a shared coupling electrode. According to the prior art, optimum performance for frequencies f1 and f2 to be received by first and second antennas, occurs at specific lengths of coupling electrode. So a shared coupling electrode may lead to a compromise in performance.
In the second embodiment, two broadband antennas according to the first embodiment are placed side-by-side. So the surface contact is larger and more expensive and harder to conceal than in the first embodiment.
In the third embodiment, two coupling electrodes according to the first embodiment are placed at 90 degrees to each other and overlapping each other. The two coupling electrodes are in direct current isolation from each other and in alternating current isolation from each other. Due to the orientation at 90 degrees, the surface contact is larger, more expensive and harder to conceal than in the first embodiment. Furthermore the shape may protrude further from the edge of the glazing towards the centre, partly obscuring a vision area of the glazing.
It is desirable to find an improved means of electrical connection of external circuits to multiple antennas on a glazing having a surface contact, the surface contact being small and having a shape that does not obscure the vision area. The object of the present invention is to provide such an improved means of electrical connection.